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Omega2+ pin headers: Are any of the pins on the pin headers also used for the MicroSD card?

  • I asked separately about the schematics but if those aren't available would someone know if any, and if so which, pins on the Omega2+ pin headers are also used for the MicroSD card? I'd like to make use of a number of the header pins for various things but also ensure that I'm not breaking MicroSD support.

  • @Chris-Morgan According to @Onion (so theoretically 😉 there aren't any differences between the Omega2(+) and the Omega2S(+) boards under the shielding.
    I think the schematics of the Omega2S Development Kits should be a good starting point to you.

    See also this thread Omega 2 Bottom Connector

  • HI @György-Farkas.

    Looking at the Omega2S-reference schematic it looks like the SD card pins are entirely separate pins but its tough to know for certain without the Omega2 module schematic I think.

    I'm using a lot of header pins (not the SPI ones related to the internal memory) but if none are related to the microSD then I'm left with an issue with this particular Omega2+ module, a firmware difference (both are upgraded to latest, I upgraded the working module once it worked thinking maybe it would break after the upgrade), or some pin configuration that isn't documented that I'm missing.... any ideas?

    The symptom I'm seeing is the kernel driver is reporting that there is no support for the card's volts. This same card works fine in my other Omega2 (not mounted on my custom PCB).

    4.901374] MTK MSDC device init.
    [    4.944622] mtk-sd: MediaTek MT6575 MSDC Driver
    [    4.954890] sdhci: Secure Digital Host Controller Interface driver
    [    4.961182] sdhci: Copyright(c) Pierre Ossman
    [    4.966206] mtk-sd 10130000.sdhci: no support for card's volts
    [    4.972137] mmc0: error -22 whilst initialising SDIO card
    [    4.978735] sdhci-pltfm: SDHCI platform and OF driver helper
    [    4.989205] usbcore: registered new interface driver usb-storage
    [    4.998530] mtk-sd 10130000.sdhci: no support for card's volts
    [    5.004520] mmc0: error -22 whilst initialising MMC card
    [    5.010722] kmodloader: done loading kernel modules from /etc/modules-boot.d/*
    [    5.020594] init: - preinit -
    [    5.254946] mtk-sd 10130000.sdhci: no support for card's volts
    [    5.260882] mmc0: error -22 whilst initialising SDIO card
    [    5.356121] mtk-sd 10130000.sdhci: no support for card's volts
    [    5.362058] mmc0: error -22 whilst initialising MMC card
    [    5.600540] mtk-sd 10130000.sdhci: no support for card's volts
    [    5.606528] mmc0: error -22 whilst initialising SDIO card
    [    5.626395] mtk-sd 10130000.sdhci: no support for card's volts
    [    5.632331] mmc0: error -22 whilst initialising MMC card

  • @Chris-Morgan I can not reproduce your issue. I guess: it is probably a HW related thing.
    Let's say you have a (low voltage???) card and the output high level of its data pins are about 1.95V or less.
    The VIHmin of the MT7688 GPIO pins are 2.0V. I think this card can work on an Omega2+ and can not work on the other one.
    This can be a "Grenzwert" "Grenzfall" (in German - sorry, I don't know the right English word).

    This may be the answer for your original question:
    the GPIO22 ... GPIO29 pins are connected / exposed only to the SD Card connector on the bottom side of the Omega2+ board.
    Mediatek MT7688 Datasheet
    0_1545500465166_MT7688 SD pin share scheme.png

  • Hi @György-Farkas.

    Same SD card works fine on another Omega2+ so I'm less likely to think its the card. Supply voltage looks good as well, 3.45v (need to adjust regulator resistors to bring that down to 3.3v) That's a good path to check and more data sheet driven then my approach of swapping the cards and performing a functional check.

    I saw that diagram with those pinouts as well but isn't EPHY_APGIO_AIO_EN set in software and not affected by the boot pins?

    After a few hours of experimenting here the issue turned out to be a relatively strong pulldown on GPIO45. This was affecting a boot pin. Looking at http://plan44.ch/downloads/Onion-Omega2-Pinout-annotated.png and the MT7688 data sheet though it isn't clear exactly what the issue is. Measuring the module itself there is a 4.7k pullup to 3.3V on that pin, so no need for external strapping. Pulling that pin down would appear to be enabling JTAG mode, page 33 of the MT7688 data sheet fyi.

    JTAG pins look entirely separate from SD interface pins though so maybe I'm close on the bootstrap pin issue but off on the effect? I still can't figure out why everything would boot fine if that GPIO45 was strapped low (overriding the 4.7k pullup) but just the SD card wouldn't be working......

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